The low Pt electrode is an important research topic for the commercialization of polymer electrolyte fuel cell (PEFC). Platinum nanoparticles act as a catalyst for the fuel cell electrode and promote the oxygen reduction reaction (ORR). In this process, the surface properties and structure of adjacent carbon supports and ionomer binders greatly affect the Pt catalyst. Therefore, the performance of the Pt/C catalyst in the fuel cell electrode is determined not only by the intrinsic activity of the catalyst itself, but also by the interface structure between the ionomer binder and the Pt/C catalyst. It has been reported that the ORR activity of the Pt/C catalyst in the fuel cell electrode is affected by the Pt poisoning of the sulfonic acid group tethered to the Nafion backbone as well as the oxygen permeability of the ionomer binder [1]. The difference in pore characteristics of the carbon support affects the optimum ionomer content [2] and Pt utilizaton [3] in the electrode. The surface properties of the carbon support also affect ionomer distribution and ionomer thickness on the catalyst surface, thereby altering the activity of the catalyst [4]. In spite of recent studies, understanding of complicated physicochemical phenomena in the microstructure of electrode is still very limited.

In this talk, we will discuss the fuel cell performance characteristics based on several electrochemical analyses according to the microstructure control of the catalyst layer. Various functional groups were introduced on the surface of Pt/C catalyst by post treatment and the catalyst layer was prepared to observe the ionomer distribution and ion transport characteristics according to functional groups. In addition, a multilayer catalyst layer having different ionomer contents in the thickness direction of the catalyst layer was prepared using an ultrasonic spraying process, and changes in hydrogen ion transfer and oxygen diffusion transfer characteristics in these catalyst layers were observed in a fuel cell. Finally, the electrochemical properties of the catalyst layer made of the ionomer dispersed in the high-boiling organic solvent will be introduced.

1. V. Yarlagadda, M. K. Carpenter, T. E. Moylan, R. S. Kukreja, R. Koestner, W. Gu, L. Thompson, A. Kongkanand, ACS Energy Lett. 3 (2018) 618.

2. Y. Liu, C. Ji, W. Gu, J. Jorne, H. A. Gasteiger, J. Electrochem. Soc. 158(6) (2011) B614.

3. Y.-C. Park, H. Tokiwa, K. Kakinuma, M. Watanabe, M. Uchida, J. Power Sources 315 (2016) 179.

4. A. Orfanidi, P. Madkikar, H. A. El-Sayed, G. S. Harzer, T. Kratky, H. A. Gasteiger, J. Electrochem. Soc. 164 (2017) F418.